Creep Cracking in 2219-T851 Plate at Elevated Temperatures

The susceptibility of 2219 to time-dependent (creep) crack growth under sustained load has been evaluated, and, while no crack growth was observed at room temperature, it was observed at elevated temperatures at stress intensities (KIcc) well below KIc. It appears that creep cracking will take place at stress intensities down to a threshold, designated KIcct, about 40 percent of KIc at 300°F, and preliminary check tests suggest that similar behavior would be in evidence at 212 and 350°F in both the L-T and T-L orientations, though much work remains to be done in defining the extent of the temperature dependence. The rate of crack growth is controlled primarily by the instantaneous stress intensity factor and can be described by the following relationship: log da/dt = 0.085K - 4.14.